Dart by Example: Lexical Scope

Dart is a lexically scoped language. Loops that declare their variable will have a new version of that variable for each iteration.

main() {
  var functions = [];

  for (var i = 0; i < 3; i++) {
    functions.add(() => i);
  }

  functions.forEach((fn) => print(fn()));

}

$ dart lexical_scope.dart
0
1
2

Compared to javascript:

var functions = [];

for (var i = 0; i < 3; i++) {
    functions[i] = function() { return i };
}

functions.forEach(function (fn) { console.log(fn())});

$ node lexical_scope.js
3
3
3